ASTM A350 LF2 NACE MR 0175 For Flanges
Exploring Low Temperature Carbon Steel LTCS ASTM A350 LF2.
ASTM A350 LF2 is a low-temperature carbon steel forged grade material widely recognized for its exceptional toughness, impact strength, and corrosion resistance in cryogenic and low-temperature applications. As part of the ASTM A350 specification, LF2 is specifically designed for use in environments where temperatures can drop below -50°F (-46°C), making it suitable for industries such as oil and gas, petrochemical, chemical processing, and power generation.
This ASTM A350 LF2 grade of carbon steel is commonly used for manufacturing flanges, fittings, valves, and other pressure-containing components subjected to low-temperature service conditions. With its robust mechanical properties and reliable performance, ASTM A350 LF2 plays a critical role in ensuring the integrity and safety of piping systems, particularly in cryogenic storage tanks, LNG (liquefied natural gas) facilities, and refrigeration applications.
ASTM A350 LF2 Chemical Composition
| Element | Composition |
|---|---|
| Carbon, max | 0.30 |
| Manganese | 0.60 – 1.35 |
| Phosphorus, max | 0.035 |
| Sulfur, max | 0.040 |
| Silicon [Note A] | 0.15 – 0.30 |
| Nickel | 0.40 max [Note B] |
| Chromium | 0.30 max [Note B,C] |
| Molybdenum | 0.12 max [Note B,C] |
| Copper | 0.40 max [Note B] |
| Columbium | 0.02 max [Note B] |
| Vanadium | 0.08 max |
Note:
A: When vacuum carbon-deoxidation is required by Supplementary Requirement S4, the silicon content shall be 0.12 % maximum.
B:The sum of copper, nickel, chromium, vanadium and molybdenum shall not exceed 1.00 % on heat analysis.
C:The sum of chromium and molybdenum shall not exceed 0.32 % on heat analysis.
D:By agreement, the limit for columbium may be increased up to 0.05 % on heat analysis and 0.06 % on product analysis.
ASTM A350 LF2 Mechanical Properties
| Tensile Strength, ksi [MPa] | Yield Strength, min, ksi [MPa] [Note B, C] | Elongation | Reduction of Area, min, % | |
|---|---|---|---|---|
| Round Specimen in 4D, min, % | Strip Specimen in 2 Inch [50mm], min, % | |||
| 70–95 [485–655] |
36 [250] | 22 | 30 | 30 |
There are 2 classes under ASTM A350/ ASME SA-350 grade LF2,
ASME SA-350 grade LF2 CL1,ASME SA-350 grade LF2 CL2.
Here are the main differences between ASTM A350 LF2 Class 1 (CL1) and Class 2 (CL2):
- Chemical Composition:
- ASTM A350 LF2 Class 1 & ASTM A350 LF2 Class 2 share the same chemical composition.
- Heat Treatment:
- Both
- ASTM A350 LF2 Class 1 & ASTM A350 LF2 Class 2 grade typically undergoes a normalizing or quenching and tempering heat treatment process to achieve
- Impact Testing Requirements:
- LF2 CL1: LF2 Class 1 requires impact testing at -46°C (-50°F) to ensure adequate toughness at low temperatures.
- LF2 CL2: LF2 Class 2 has more stringent impact testing requirements, requiring testing at lower temperatures, typically at -18°C (-0°F), to demonstrate superior toughness characteristics.
- Tensile Strength:ASTM A350 LF2 Class 1 & ASTM A350 LF2 Class 2 have the same Tensile Strength:.
- Applications:
- Both LF2 CL1 and CL2 are commonly used in low-temperature and cryogenic applications such as pressure vessels, piping systems, and valves in industries including oil and gas, chemical processing, and power generation.
Generally, Class 1 and Class 2 of ASTM A350/ ASME SA-350 grade LF2 have the same chemical composition and mechanical properties. Even the allowable stresses of Class 1 and Class 2 in ASME Codes are the same. The main characteristic that distinguishes Class 1 from Class 2 is its minimum applicable temperature. The minimum applicable temperatures are -50°F [-46°C] for LF2 Class 1 and -0°F [-18°C] for LF2 Class 2, respectively.
ASTM A350 LF2 Hardness requirement:
ASTM A350 LF2 requires the hardness to be 197 HB maximum, and this meets the requirements for carbon steel forgings in NACE MR0175/ISO 15156-2.
ASTM A350 LF2 Flange Manufacuring Process
Melting Process—The steel shall be produced by any of the following primary processes: open-hearth, basic oxygen, electric-furnace, or vacuum-induction melting (VIM). The primary melting may incorporate separate degassing or refining, and may be followed by secondary melting using electroslag remelting (ESR), or vacuum-arc remelting (VAR).
ASTM A350 LF2 steel shall be fully killed, fine-grain practice.
The molten steel may be vacuum treated prior to or during pouring of the ingot.
Discard—A sufficient discard shall be made to secure freedom from injurious piping and undue segregation.
Forging Process: Material for forgings shall consist of ingots, or forged, rolled, or strandcast blooms, billets, slabs, or bars.
The finished product shall be a forging as defined in the Terminology section of Specification A788/A788M.
Flanges
A pipe flange is parts used for connection the pipes or fittings.The flanges can be a disc, collar, or ring that attaches to the end of a pipe.
ASTM A350 LF2 is a pupular grade for the flanges used for low temperature pipeline connections.
These flanges include socket weld flanges, blind flanges, weld-decked flanges and slip-on flanges, etc. The flanges provide the surface for sealing the gasket against applied forces and moving it around the gasket. The connection will allow easy disassembly and reassembly of pipes or removal of components.
ASTM A350 LF2 Flange Supply Scope:
Grades: ASTM A350/ ASME SA350 Grade LF2 Class 1, 2
Size: 1/2” to 24” in ASME B16.5, up to 60” in ASME B16.47
Pressure Class: Class 150, 300, 600, 900, 1500, 2500
Manufacturing Standards:ASTM A350 ASME B16.5, ASME B16.47 A, B
